/*
Copyright 2021 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package common

import (
	"bytes"
	"crypto/hmac"
	"crypto/sha1"
	"crypto/sha256"
	"encoding/base64"
	"encoding/hex"
	"hash"
	"sort"

	tchttp "k8s.io/autoscaler/cluster-autoscaler/cloudprovider/tencentcloud/tencentcloud-sdk-go/common/http"
)

const (
	SHA256 = "HmacSHA256"
	SHA1   = "HmacSHA1"
)

func Sign(s, secretKey, method string) string {
	var hashed hash.Hash
	switch method {
	case SHA256:
		hashed = hmac.New(sha256.New, []byte(secretKey))
	default:
		hashed = hmac.New(sha1.New, []byte(secretKey))
	}
	hashed.Write([]byte(s))

	return base64.StdEncoding.EncodeToString(hashed.Sum(nil))
}

func sha256hex(s string) string {
	b := sha256.Sum256([]byte(s))
	return hex.EncodeToString(b[:])
}

func hmacsha256(s, key string) string {
	hashed := hmac.New(sha256.New, []byte(key))
	hashed.Write([]byte(s))
	return string(hashed.Sum(nil))
}

func signRequest(request tchttp.Request, credential CredentialIface, method string) (err error) {
	if method != SHA256 {
		method = SHA1
	}
	checkAuthParams(request, credential, method)
	s := getStringToSign(request)
	signature := Sign(s, credential.GetSecretKey(), method)
	request.GetParams()["Signature"] = signature
	return
}

func checkAuthParams(request tchttp.Request, credential CredentialIface, method string) {
	params := request.GetParams()
	params["SecretId"] = credential.GetSecretId()
	if token := credential.GetToken(); len(token) != 0 {
		params["Token"] = token
	}
	params["SignatureMethod"] = method
	delete(params, "Signature")
}

func getStringToSign(request tchttp.Request) string {
	method := request.GetHttpMethod()
	domain := request.GetDomain()
	path := request.GetPath()

	var buf bytes.Buffer
	buf.WriteString(method)
	buf.WriteString(domain)
	buf.WriteString(path)
	buf.WriteString("?")

	params := request.GetParams()
	// sort params
	keys := make([]string, 0, len(params))
	for k := range params {
		keys = append(keys, k)
	}
	sort.Strings(keys)

	for i := range keys {
		k := keys[i]
		buf.WriteString(k)
		buf.WriteString("=")
		buf.WriteString(params[k])
		buf.WriteString("&")
	}
	buf.Truncate(buf.Len() - 1)
	return buf.String()
}
